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Article: Effect of Carbon Nanofiber Clustering on the Micromechanical Properties of a Cement Paste.

Brown, Lesa / Stephens, Catherine S / Allison, Paul G / Sanchez, Florence

2022 Volume 12, Issue 2

Abstract: The use of carbon nanofibers (CNFs) in cement systems has received significant interest over the last decade due to their nanoscale reinforcing potential. However, despite many reports on the formation of localized CNF clusters, their effect on the ... ...

Abstract	The use of carbon nanofibers (CNFs) in cement systems has received significant interest over the last decade due to their nanoscale reinforcing potential. However, despite many reports on the formation of localized CNF clusters, their effect on the cement paste micromechanical properties and relation to the mechanical response at the macroscopic scale are still not fully understood. In this study, grid nanoindentation coupled with scanning electron microscopy and energy dispersive spectroscopy was used to determine the local elastic indentation modulus and hardness of a portland cement paste containing 0.2% CNFs with sub-micro and microscale CNF clusters. The presence of low stiffness and porous assemblage of phases (modulus of 15-25 GPa) was identified in the cement paste with CNFs and was attributed primarily to the interfacial zone surrounding the CNF clusters. The CNFs favored the formation of higher modulus C-S-H phases (>30 GPa) in the bulk paste at the expense of the lower stiffness C-S-H. Nanoindentation results combined with a microscale-macroscale upscaling homogenization method further revealed an elastic modulus of the CNF clusters in the range from 18 to 21 GPa, indicating that the CNF clusters acted as compliant inclusions relative to the cement paste.
Language	English
Publishing date	2022-01-10
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2662255-5
ISSN	2079-4991
ISSN	2079-4991
DOI	10.3390/nano12020223
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Article: Microstructure and Mechanical Behavior Comparison between Cast and Additive Friction Stir-Deposited High-Entropy Alloy Al

McClelland, Zackery / Dunsford, Kyle / Williams, Brady / Petersen, Haley / Devami, Keivan / Weaver, Mark / Jordan, J Brian / Allison, Paul G

Materials (Basel, Switzerland)

2024 Volume 17, Issue 4

Abstract: High-entropy alloys (HEAs) are new alloy systems that leverage solid solution strengthening to develop high-strength structural materials. However, HEAs are typically cast alloys, which may suffer from large as-cast grains and entrapped porosity, ... ...

Abstract	High-entropy alloys (HEAs) are new alloy systems that leverage solid solution strengthening to develop high-strength structural materials. However, HEAs are typically cast alloys, which may suffer from large as-cast grains and entrapped porosity, allowing for opportunities to further refine the microstructure in a non-melting near-net shape solid-state additive manufacturing process, additive friction stir deposition (AFSD). The present research compares the microstructure and mechanical behavior of the as-deposited AFSD Al
Language	English
Publishing date	2024-02-16
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2487261-1
ISSN	1996-1944
ISSN	1996-1944
DOI	10.3390/ma17040910
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Article: Microstructural and Mechanical Characterization of Additive Friction Stir-Deposition of Aluminum Alloy 5083 Effect of Lubrication on Material Anisotropy.

Phillips, Brandon J / Williamson, C Jacob / Kinser, Ryan P / Jordon, J Brian / Doherty, Kevin J / Allison, Paul G

Materials (Basel, Switzerland)

2021 Volume 14, Issue 21

Abstract: Additive Friction Stir-Deposition (AFS-D) is a transformative, metallic additive manufacturing (AM) process capable of producing near-net shape components with a wide variety of material systems. The solid-state nature of the process permits many of ... ...

Abstract	Additive Friction Stir-Deposition (AFS-D) is a transformative, metallic additive manufacturing (AM) process capable of producing near-net shape components with a wide variety of material systems. The solid-state nature of the process permits many of these materials to be successfully deposited without the deleterious phase and thermally activated defects commonly observed in other metallic AM technologies. This work is the first to investigate the as-deposited microstructure and mechanical performance of a free-standing AA5083 deposition. An initial process parameterization was conducted to down-select optimal parameters for a large deposition to examine build direction properties. Microscopy revealed that constitutive particles were dispersed evenly throughout the matrix when compared to the rolled feedstock. Electron backscatter diffraction revealed a significant grain refinement from the inherent dynamic recrystallization from the AFS-D process. Tensile experiments determined a drop in yield strength, but an improvement in tensile strength in the longitudinal direction. However, a substantial reduction in tensile strength was observed in the build direction of the structure. Subsequent fractographic analysis revealed that the recommended lubrication applied to the feedstock rods, necessary for successful depositions via AFS-D, was ineffectively dispersed into the structure. As a result, lubrication contamination became entrapped at layer boundaries, preventing adequate bonding between layers.
Language	English
Publishing date	2021-11-08
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2487261-1
ISSN	1996-1944
ISSN	1996-1944
DOI	10.3390/ma14216732
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Article ; Online: Finite element modeling of multilayered structures of fish scales.

Chandler, Mei Qiang / Allison, Paul G / Rodriguez, Rogie I / Moser, Robert D / Kennedy, Alan J

Journal of the mechanical behavior of biomedical materials

2014 Volume 40, Page(s) 375–389

Abstract: The interlinked fish scales of Atractosteus spatula (alligator gar) and Polypterus senegalus (gray and albino bichir) are effective multilayered armor systems for protecting fish from threats such as aggressive conspecific interactions or predation. Both ...

Abstract	The interlinked fish scales of Atractosteus spatula (alligator gar) and Polypterus senegalus (gray and albino bichir) are effective multilayered armor systems for protecting fish from threats such as aggressive conspecific interactions or predation. Both types of fish scales have multi-layered structures with a harder and stiffer outer layer, and softer and more compliant inner layers. However, there are differences in relative layer thickness, property mismatch between layers, the property gradations and nanostructures in each layer. The fracture paths and patterns of both scales under microindentation loads were different. In this work, finite element models of fish scales of A. spatula and P. senegalus were built to investigate the mechanics of their multi-layered structures under penetration loads. The models simulate a rigid microindenter penetrating the fish scales quasi-statically to understand the observed experimental results. Study results indicate that the different fracture patterns and crack paths observed in the experiments were related to the different stress fields caused by the differences in layer thickness, and spatial distribution of the elastic and plastic properties in the layers, and the differences in interface properties. The parametric studies and experimental results suggest that smaller fish such as P. senegalus may have adopted a thinner outer layer for light-weighting and improved mobility, and meanwhile adopted higher strength and higher modulus at the outer layer, and stronger interface properties to prevent ring cracking and interface cracking, and larger fish such as A. spatula and Arapaima gigas have lower strength and lower modulus at the outer layers and weaker interface properties, but have adopted thicker outer layers to provide adequate protection against ring cracking and interface cracking, possibly because weight is less of a concern relative to the smaller fish such as P. senegalus.
MeSH term(s)	Animals ; Finite Element Analysis ; Fishes ; Models, Biological ; Skin/chemistry ; Stress, Mechanical
Language	English
Publishing date	2014-12
Publishing country	Netherlands
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2378381-3
ISSN	1878-0180 ; 1751-6161
ISSN (online)	1878-0180
ISSN	1751-6161
DOI	10.1016/j.jmbbm.2014.09.013
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Article ; Online: Gastropod (Otala lactea) shell nanomechanical and structural characterization as a biomonitoring tool for dermal and dietary exposure to a model metal.

Allison, Paul G / Seiter, Jennifer M / Diaz, Alfredo / Lindsay, James H / Moser, Robert D / Tappero, Ryan V / Kennedy, Alan J

Journal of the mechanical behavior of biomedical materials

2016 Volume 53, Page(s) 142–150

Abstract: Metallic tungsten (W) was initially assumed to be environmentally benign and a green alternative to lead. However, subsequent investigations showed that fishing weights and munitions containing elemental W can fragment and oxidize into complex monomeric ... ...

Abstract	Metallic tungsten (W) was initially assumed to be environmentally benign and a green alternative to lead. However, subsequent investigations showed that fishing weights and munitions containing elemental W can fragment and oxidize into complex monomeric and polymeric tungstate (WO4) species in the environment; this led to increased solubility and mobility in soils and increased bioaccumulation potential in plant and animal tissues. Here we expand on the results of our previous research, which examined tungsten toxicity, bioaccumulation, and compartmentalization into organisms, and present in this research that the bioaccumulation of W was related to greater than 50% reduction in the mechanical properties of the snail (Otala lactea), based on depth-sensing nanoindentation. Synchrotron-based X-ray fluorescence maps and X-ray diffraction measurements confirm the integration of W in newly formed layers of the shell matrix with the observed changes in shell biomechanical properties, mineralogical composition, and crystal orientation. With further development, this technology could be employed as a biomonitoring tool for historic metals contamination since unlike the more heavily studied bioaccumulation into soft tissue, shell tissue does not actively eliminate contaminants.
MeSH term(s)	Animal Shells/drug effects ; Animal Shells/metabolism ; Animals ; Biomechanical Phenomena/drug effects ; Diet/adverse effects ; Environmental Monitoring/methods ; Environmental Pollutants/metabolism ; Environmental Pollutants/toxicity ; Gastropoda/anatomy & histology ; Gastropoda/drug effects ; Gastropoda/metabolism ; Mechanical Phenomena ; Nanotechnology/methods ; Skin/drug effects ; Skin/metabolism ; Tungsten/metabolism ; Tungsten/toxicity
Chemical Substances	Environmental Pollutants ; Tungsten (V9306CXO6G)
Language	English
Publishing date	2016-01
Publishing country	Netherlands
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2378381-3
ISSN	1878-0180 ; 1751-6161
ISSN (online)	1878-0180
ISSN	1751-6161
DOI	10.1016/j.jmbbm.2015.08.016
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Article ; Online: Tungsten toxicity, bioaccumulation, and compartmentalization into organisms representing two trophic levels.

Kennedy, Alan J / Johnson, David R / Seiter, Jennifer M / Lindsay, James H / Boyd, Robert E / Bednar, Anthony J / Allison, Paul G

Environmental science & technology

2012 Volume 46, Issue 17, Page(s) 9646–9652

Abstract: Metallic tungsten has civil and military applications and was considered a green alternative to lead. Recent reports of contamination in drinking water and soil have raised scrutiny and suspended some applications. This investigation employed the cabbage ...

Abstract	Metallic tungsten has civil and military applications and was considered a green alternative to lead. Recent reports of contamination in drinking water and soil have raised scrutiny and suspended some applications. This investigation employed the cabbage Brassica oleracae and snail Otala lactea as models to determine the toxicological implications of sodium tungstate and an aged tungsten powder-spiked soil containing monomeric and polymeric tungstates. Aged soil bioassays indicated cabbage growth was impaired at 436 mg of W/kg, while snail survival was not impacted up to 3793 mg of W/kg. In a dermal exposure, sodium tungstate was more toxic to the snail, with a lethal median concentration of 859 mg of W/kg. While the snail significantly bioaccumulated tungsten, predominately in the hepatopancreas, cabbage leaves bioaccumulated much higher concentrations. Synchrotron-based mapping indicated the highest levels of W were in the veins of cabbage leaves. Our results suggest snails consuming contaminated cabbage accumulated higher tungsten concentrations relative to the concentrations directly bioaccumulated from soil, indicating the importance of robust trophic transfer investigations. Finally, synchrotron mapping provided evidence of tungsten in the inner layer of the snail shell, suggesting potential use of snail shells as a biomonitoring tool for metal contamination.
MeSH term(s)	Animals ; Brassica/drug effects ; Brassica/growth & development ; Brassica/metabolism ; Environmental Monitoring ; Snails/drug effects ; Snails/metabolism ; Snails/physiology ; Soil Pollutants/analysis ; Soil Pollutants/metabolism ; Soil Pollutants/toxicity ; Tungsten/analysis ; Tungsten/metabolism ; Tungsten/toxicity ; Tungsten Compounds/analysis ; Tungsten Compounds/metabolism ; Tungsten Compounds/toxicity
Chemical Substances	Soil Pollutants ; Tungsten Compounds ; Tungsten (V9306CXO6G)
Language	English
Publishing date	2012-09-04
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ISSN	1520-5851
ISSN (online)	1520-5851
DOI	10.1021/es300606x
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Article: Tungsten Toxicity, Bioaccumulation, and Compartmentalization into Organisms Representing Two Trophic Levels

Kennedy, Alan J / Allison Paul G / Bednar Anthony J / Boyd Robert E / Johnson David R / Lindsay James H / Seiter Jennifer M

Environmental Science & Technology. 2012 Sept. 04, v. 46, no. 17

2012

Abstract	Metallic tungsten has civil and military applications and was considered a green alternative to lead. Recent reports of contamination in drinking water and soil have raised scrutiny and suspended some applications. This investigation employed the cabbage Brassica oleracae and snail Otala lactea as models to determine the toxicological implications of sodium tungstate and an aged tungsten powder-spiked soil containing monomeric and polymeric tungstates. Aged soil bioassays indicated cabbage growth was impaired at 436 mg of W/kg, while snail survival was not impacted up to 3793 mg of W/kg. In a dermal exposure, sodium tungstate was more toxic to the snail, with a lethal median concentration of 859 mg of W/kg. While the snail significantly bioaccumulated tungsten, predominately in the hepatopancreas, cabbage leaves bioaccumulated much higher concentrations. Synchrotron-based mapping indicated the highest levels of W were in the veins of cabbage leaves. Our results suggest snails consuming contaminated cabbage accumulated higher tungsten concentrations relative to the concentrations directly bioaccumulated from soil, indicating the importance of robust trophic transfer investigations. Finally, synchrotron mapping provided evidence of tungsten in the inner layer of the snail shell, suggesting potential use of snail shells as a biomonitoring tool for metal contamination.
Keywords	bioaccumulation ; bioassays ; Brassica ; cabbage ; dermal exposure ; drinking water ; environmental monitoring ; hepatopancreas ; leaves ; models ; shell (molluscs) ; snails ; soil ; toxicity ; trophic levels ; tungsten
Language	English
Dates of publication	2012-0904
Size	p. 9646-9652.
Publishing place	American Chemical Society
Document type	Article
ISSN	1520-5851
DOI	10.1021%2Fes300606x
Database	NAL-Catalogue (AGRICOLA)

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Article: Characterization of multi-layered fish scales (Atractosteus spatula) using nanoindentation, x-ray ct, ftir, and sem

Allison, Paul G / Rodriguez, Rogie I / Moser, Robert D / Williams, Brett A / Poda, Aimee R / Seiter, Jennifer M / Lafferty, Brandon J / Kennedy, Alan J / Chandler, Mei Q

Journal of visualized experiments. 2014 July 10, , no. 89

2014

Abstract: The hierarchical architecture of protective biological materials such as mineralized fish scales, gastropod shells, ram’s horn, antlers, and turtle shells provides unique design principles with potentials for guiding the design of protective materials ... ...

Abstract	The hierarchical architecture of protective biological materials such as mineralized fish scales, gastropod shells, ram’s horn, antlers, and turtle shells provides unique design principles with potentials for guiding the design of protective materials and systems in the future. Understanding the structure-property relationships for these material systems at the microscale and nanoscale where failure initiates is essential. Currently, experimental techniques such as nanoindentation, X-ray CT, and SEM provide researchers with a way to correlate the mechanical behavior with hierarchical microstructures of these material systems1-6. However, a well-defined standard procedure for specimen preparation of mineralized biomaterials is not currently available. In this study, the methods for probing spatially correlated chemical, structural, and mechanical properties of the multilayered scale of A. spatula using nanoindentation, FTIR, SEM, with energy-dispersive X-ray (EDX) microanalysis, and X-ray CT are presented.
Keywords	Atractosteus spatula ; Fourier transform infrared spectroscopy ; Gastropoda ; antlers ; biocompatible materials ; computed tomography ; energy-dispersive X-ray analysis ; mechanical properties ; microstructure ; mineralization ; rams ; scales (integument) ; scanning electron microscopy ; turtles
Language	English
Dates of publication	2014-0710
Size	p. e51535.
Publishing place	Journal of Visualized Experiments
Document type	Article
ZDB-ID	2259946-0
ISSN	1940-087X
ISSN	1940-087X
DOI	10.3791/51535
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Characterization of multi-layered fish scales (Atractosteus spatula) using nanoindentation, X-ray CT, FTIR, and SEM.

Allison, Paul G / Rodriguez, Rogie I / Moser, Robert D / Williams, Brett A / Poda, Aimee R / Seiter, Jennifer M / Lafferty, Brandon J / Kennedy, Alan J / Chandler, Mei Q

Journal of visualized experiments : JoVE

2014 , Issue 89

Abstract: The hierarchical architecture of protective biological materials such as mineralized fish scales, gastropod shells, ram's horn, antlers, and turtle shells provides unique design principles with potentials for guiding the design of protective materials ... ...

Abstract	The hierarchical architecture of protective biological materials such as mineralized fish scales, gastropod shells, ram's horn, antlers, and turtle shells provides unique design principles with potentials for guiding the design of protective materials and systems in the future. Understanding the structure-property relationships for these material systems at the microscale and nanoscale where failure initiates is essential. Currently, experimental techniques such as nanoindentation, X-ray CT, and SEM provide researchers with a way to correlate the mechanical behavior with hierarchical microstructures of these material systems1-6. However, a well-defined standard procedure for specimen preparation of mineralized biomaterials is not currently available. In this study, the methods for probing spatially correlated chemical, structural, and mechanical properties of the multilayered scale of A. spatula using nanoindentation, FTIR, SEM, with energy-dispersive X-ray (EDX) microanalysis, and X-ray CT are presented.
MeSH term(s)	Animals ; Fishes/anatomy & histology ; Integumentary System/anatomy & histology ; Microscopy, Electron, Scanning ; Spectroscopy, Fourier Transform Infrared ; Structure-Activity Relationship ; Tomography, X-Ray Computed
Language	English
Publishing date	2014-07-10
Publishing country	United States
Document type	Journal Article ; Research Support, U.S. Gov't, Non-P.H.S. ; Video-Audio Media
ZDB-ID	2259946-0
ISSN	1940-087X ; 1940-087X
ISSN (online)	1940-087X
ISSN	1940-087X
DOI	10.3791/51535
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